1. Field of the Invention
The invention relates to a backlight module; in particular, the invention relates to a backlight module that prevents lamp and diffuser deformation.
2. Description of the Related Art
In a liquid crystal display unit of a liquid crystal display, a backlight module is generally utilized as a light source. According to the structure, the backlight module can be divided into an edge type or direct type module. Since this invention seeks to improve the direct type backlight module, the description of the edge type backlight module is omitted.
As shown in FIG. 1, a direct type backlight module 10 includes a reflector 11, a diffuser plate 12, a plurality of lamps 13, and a plurality of supporting columns 14. The reflector 11 is located at the bottom of the backlight module 10, and reflects the light from the lamps 13 out of the backlight module 10. The diffuser plate 12 is disposed on the reflector 11 in a manner such that the lamps 13 are covered by the diffuser plate 12 form the backlight. The lamps 13 are utilized as the light source of the backlight module 10. The supporting columns 14 are disposed between the reflector 11 and the diffuser 12 so as to support the diffuser plate 12. Thus, warping or deformation of the diffuser plate 12 is prevented, and the optical quality of the backlight module 10 can be maintained to a specified standard.
The backlight module 10, however, has the following disadvantage. When the size of the liquid crystal display increases, the size of the lamps in the backlight module also increases, as does the possibility of lamp deformation. Thus, the optical quality of the entire liquid crystal display suffers.
In Japanese Publication No. H05-119703, a backlight module 20 that solves the above problem is disclosed. As shown in FIG. 2, support platens 24 are additionally disposed under the lamps 23 to prevent deformation of the lamps 23. The disadvantage of the backlight module 20 is that as the size of the liquid crystal display increases, the size of the diffuser in the backlight module also increases as does the possibility of diffuser deformation. Thus, the optical quality of the entire liquid crystal display suffers.
Japanese Publication No. 2001-210126, discloses another backlight module 30. As shown in FIG. 3, supporting assemblies 34 are additionally disposed under the lamps 33 to prevent deformation of the lamps 33. Each of the supporting assemblies 34 includes a column 341 to be abutted by the diffuser 32. The diffuser 32 can be maintained at a predetermined position by the columns 341, thus the Mura effect of backlight module can be prevented.
The backlight module 30, however, has the following disadvantages. First, when the supporting assembly 34 is disposed inside the backlight module 30, the diffuser plate 32 is abutted by the columns 341. Thus, when the backlight module 30 is operated, the diffuser 32 may be projected outwardly by the expansion of the columns 341 due to increased temperature inside the backlight module 30. As a result, warping, deformation may occur in the diffuser plate 32. Second, two lamps 33 are simultaneously supported by one supporting assembly 34. When the supporting assembly 34 expands due to increased temperature, the lamps 33 may be moved relative to each other. Thus, the lamps 33 may be damaged. Moreover, the column 341 may be moved due to the thermal expansion of the supporting assembly 34 so that the diffuser 32, abutted by the column 341, may also be damaged.